Why 56 different type of food is offered to Sri Krishna? And, why not any other number of foods. The reason for Chappan Bhog (56) is associated with Sri Krishna lifting Govardhan Mountain.
As per Hindu scriptures, Mata Yashoda, foster mother of Sri Krishna, used to feed young Krishna eight times a day.
Sri Krishna advised the people of Braj not to make offering to Indra. The King of Deva, Indra, became angry and created torrential rain in Braj region.
To protect the people of Braj, Sri Krishna lifted the Govardhan Mountain using his small finger. He gave shelter to all living beings in Braj under the Govardhan Mountain.
The rains continued for 7 days. Finally, Indra had to give up and accept the order set by Sri Krishna.
Sri Krishna then asked all living beings to return to their respective abodes. He then placed the Govardhan Mountain down.
As young Sri Krishna did not eat for 7 days, all the people of Braj decided to feed him the food of all 7 days. Sri Krishna used to eat 8 times a day and so Braj people decided to feed him 56 times (8 X 7).